Function of the medial meniscus in force transmission and stability

Use of magnetic resonance imaging to determine laterality of meniscal size in healthy volunteers

Introduction

The menisci are responsible for several functions. They are shock absorbers during dynamic loading on the knee and provide a broader surface area on which to distribute stress evenly to the tibia and femur. These functions allow for smoother movement and greater stability of the knee joint. Meniscal injury can be a great impediment to the function of the knee. Therefore, in the case of meniscal injury, our main concern is the relief of patient symptoms, followed by consequent restoration of meniscal function to the greatest of our ability.

To prevent the long terms effects of a meniscectomy, meniscal allograft transplantation (MAT) was developed. The potential of using the size of the contralateral healthy menisci, to determine the size of the menisci to be replaced, will be discussed.

Methods

Knee MRIs done on healthy patients in the past 5 years were reviewed. Magnetic Resonance Imaging was performed using a 3-T scanner. Each individual was examined with knee joints in full extension. Measurements were performed two separate times, two weeks apart. A mean of three measurements was made during each session to reduce error.

Thirty-eight normal bilateral knee joints MRIs remained (16 males, 22 females). Participants were sampled from the institutional Picture Archiving and Communication System (PACS). Age, gender, and the medial meniscal and lateral meniscal size of both knees were recorded. The laterality of the menisci was compared between both knees in each patient.

Results

A total of 38 patients were included in this study, with a mean age of 37.39 (±9.50) years. They were 16 (42.1%) men and 22 (57.9%) women. We didn’t find any significant difference in the mid-coronal section between left and right knees meniscal measurements. None of the measurements were significantly different between men and women. There was no significant difference in the medial mid-sagittal section or lateral mid-sagittal section between left and right knee meniscal measurements.

Conclusion

The results obtained in this study may support the use of MRI of the bilateral knee to obtain an appropriately sized allograft.

Biomechanical analysis of the centralization procedure for extruded lateral menisci with posterior root deficiency in a porcine model

PURPOSE

The purpose of this study was to investigate the biomechanical properties of load distribution following a centralization procedure for extruded lateral menisci with posterior root deficiency in a porcine model.

METHODS

Six porcine knee joints were analyzed in a universal tester, as follows: 1) Intact; 2) Extrusion (meniscus extrusion was created by resecting the posterior root of the lateral meniscus, as well as the posterior synovial capsule); and 3) Centralization (two anchors were inserted at the lateral tibial plateau, and the meniscus was sutured to secure it close to the original position). Meniscus extrusion was evaluated using two markers put on the posterior cruciate ligament and the lateral meniscus, and the load distribution were assessed using a pressure mapping sensor system after applying a loading force of 200 N to the knee joint.

RESULTS

Distance between two markers (mm, Average; 95% CI) was larger in the extrusion group (21.9; 17.8, 25.6) than in the intact (18.1; 15.1, 22.7) or the centralization (15.3; 12.9, 18.0) groups. The contact area (mm²) in the middle of the meniscus was significantly smaller in the extrusion group (45.8; 18.5, 73.2) than in the intact (85.7; 72.1, 99.2) or the centralization (98.3; 88.8, 107.8) groups. The maximum contact pressure (MPa) in the tibial plateau was significantly higher in the extrusion group (0.37; 0.35, 0.40) than in the intact (0.29; 0.21, 0.37) or the centralization (0.29; 0.22, 0.36) groups.

CONCLUSIONS

The centralization procedure enabled a reduction of the meniscus extrusion in the lateral meniscus with posterior root deficiency and restored the maximum load and contact pressure to values close to those of the normal knee joint.

PCL-MECM-Based Hydrogel Hybrid Scaffolds and Meniscal Fibrochondrocytes Promote Whole Meniscus Regeneration in a Rabbit Meniscectomy Model

Regeneration of an injured meniscus continues to be a scientific challenge due to its poor self-healing potential. Tissue engineering provides an avenue for regenerating a severely damaged meniscus. In this study, we first investigated the superiority of five concentrations (0%, 0.5%, 1%, 2%, and 4%) of meniscus extracellular matrix (MECM)-based hydrogel in promoting cell proliferation and the matrix-forming phenotype of meniscal fibrochondrocytes (MFCs). We found that the 2% group strongly enhanced chondrogenic marker mRNA expression and cell proliferation compared to the other groups. Moreover, the 2% group showed the highest glycosaminoglycan (GAG) and collagen production by day 14. We then constructed a hybrid scaffold by 3D printing a wedge-shaped poly(ε-caprolactone) (PCL) scaffold as a backbone, followed by injection with the optimized MECM-based hydrogel (2%), which served as a cell delivery system. The hybrid scaffold (PCL-hydrogel) clearly yielded favorable biomechanical properties close to those of the native meniscus. Finally, PCL scaffold, PCL-hydrogel, and MFCs-loaded hybrid scaffold (PCL-hydrogel-MFCs) were implanted into the knee joints of New Zealand rabbits that underwent total medial meniscectomy. Six months postimplantation we found that the PCL-hydrogel-MFCs group exhibited markedly better gross appearance and cartilage protection than the PCL scaffold and PCL-hydrogel groups. Moreover, the regenerated menisci in the PCL-hydrogel-MFCs group had similar histological structures, biochemical contents, and biomechanical properties as the native menisci in the sham operation group. In conclusion, PCL-MECM-based hydrogel hybrid scaffold seeded with MFCs can successfully promote whole meniscus regeneration, and cell-loaded PCL-MECM-based hydrogel hybrid scaffold may be a promising strategy for meniscus regeneration in the future.

Effect of physical therapy on early knee osteoarthritis with medial meniscal posterior tear assessed by MRI T2 mapping and 3D-to-2D registration technique: A prospective intervention study

Objectives: The purpose of this study was to verify that exercise aimed at improving knee kinematics in early-stage knee osteoarthritis (OA) patients with medial meniscus posterior root tears (MMPRTs) reduces knee adduction angle during gait and prevents rapid cartilage degeneration in the medial compartment of the knee.Methods: Subjects were randomly assigned to an adapting alignment exercise (AAE) group, with the goal of improving knee kinematics, and a muscle training and exercise (MTE) group. Before the start of the six-month intervention and following its completion, we performed an analysis of knee kinematics during gait using a 3D-to-2D registration technique and identified the area of cartilage degeneration using MRI T2 mapping.Results: The amount of change between pre- and post-intervention measurements of the maximum angle of adduction was 0.48° (95% CI: -0.14, 1.09) in the MTE group and -0.40° (-0.84, 0.04) in the AAE group (p = .039). The amount of change in the area of cartilage degeneration according to MRI T2 mapping expressed as MTE/AAE group was 7.7 mm² (-0.4, 15.8)/-2.7 mm² (-10.8, 5.3) at the posterior knee (p = .043).Conclusion: AAE could be a potential treatment method that improves the natural course of knee OA with MMRPTs.

Anterior Cruciate Ligament Reconstruction in Young Female Athletes: Patellar Versus Hamstring Tendon Autografts

BACKGROUND

Female athletes are 2 to 8 times more prone to anterior cruciate ligament (ACL) rupture than males. Furthermore, reinjury to the ipsilateral or contralateral knee can occur in >20% of athletes. Female sex and younger age are known risk factors for graft failure. The optimal graft choice for young females remains unknown and poorly studied.

PURPOSE/HYPOTHESIS

The authors aimed to compare clinical outcomes in young females who underwent ACL reconstruction (ACLR) with bone-patellar tendon-bone (BTB) and quadrupled hamstring (HS) autografts. It was hypothesized that no significant differences in outcomes exist between graft choices.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Female patients aged 15 to 25 years who underwent primary ACLR with BTB or HS autograft were included for review. Patients were subdivided into 2 age groups: 15 to 20 years and 21 to 25 years. The occurrence of chondral, meniscal, or ligamentous injury to either knee was recorded for comparison.

RESULTS

A total of 256 females were included (BTB, n = 175; HS, n = 81). The majority of patients were between the ages of 15 and 20 years (BTB, 80%; HS, 77.8%). Overall, graft rupture occurred in 23 patients (9%) and contralateral ACL tear occurred in 18 (7%). Subgroup analysis showed that 75% of BTB and 100% of HS graft retears occurred in females aged 15 to 20 years. Within this age group, there was a significantly lower rate of graft ruptures in the BTB group (6.4%) as compared with the HS group (17.5%, P = .02). Allograft augmentation was used in 4 of the 11 HS grafts that retore. When allograft-augmented grafts were excluded, there was no significant difference in graft failure rate between graft choices. Fifteen patients in the BTB group (12%) as opposed to 1 in the HS group (2%) reported extreme difficulty or the inability to kneel on the front of the knee (P = .04).

CONCLUSION

In females aged 15 to 20 years undergoing ACLR, BTB autograft may lead to fewer graft ruptures than HS autograft. While this difference was not observed in females aged 21 to 25 years, a larger sample may be required to accept the null hypothesis in this age group. BTB autograft significantly increased the risk of kneeling pain as compared with HS regardless of age.

Dynamic intraligamentary stabilization of anterior cruciate ligament repair: hardware removal has no effect on knee laxity at 2-year follow-up

INTRODUCTION

Dynamic intraligamentary stabilization (DIS) stabilizes the knee joint during anterior cruciate ligament (ACL) healing. After 6 months, tibial hardware removal is offered to the patients if local discomfort at the implant site is present.

AIM

This study compared knee laxity and functional scores 2 years after DIS between patients with and without hardware removal. It is hypothesized that it does not affect ACL healing.

MATERIALS AND METHODS

The study retrospectively analyzed prospectively collected data from 173 patients with either hardware removal (n = 47) or no additional intervention (n = 126). Inverse probability of treatment weighting using the propensity score was applied to balance the groups for baseline characteristics. The primary outcome was the side-to-side difference in knee laxity measured with the rolimeter at manual maximum force (Δ-Lachman). Secondary outcomes were the pivot-shift test and subjective scores.

RESULTS

Mean age was 34 years in both groups, and female gender was 47% (hardware removal group) and 50% (control group), respectively. No significant differences were found for Δ-Lachman (p = 0.09), pivot-shift test (p = 0.41), and subjective scores (p > 0.10) two years after DIS.

CONCLUSION

Knee laxity 2 years after DIS in patients with tibial hardware removal and patients without hardware removal was not significantly different. The groups were also similar regarding all the assessed functional scores. This study confirms the hypothesis that the healing ACL resumes its stabilizing role, and the hardware can be removed beginning 6 months after surgery without adverse consequences for joint stability.

LEVEL OF EVIDENCE

Case-control study, Level III.

The role of menisci in knee contact mechanics and secondary kinematics during human walking

BACKGROUND

Meniscectomy is likely to result in an increase of joint loading on articular cartilage and initiates cartilage damages. However, the induced alterations in knee contact mechanics and secondary kinematics after the meniscal removal are still unclear during a walking gait. In this study, the role of menisci on the knee contact mechanics and secondary kinematics were investigated during a walking simulation.

METHODS

Two natural knee models with or without menisci were established using a musculoskeletal multibody dynamics framework. Walking simulation were performed to qualify the knee contact forces and secondary kinematics, and ligament forces in these models.

FINDINGS

After the meniscal removal, the redistributed contact forces on the medial tibial cartilage increased by twofold, while the contact area remained almost the same. The subsequent increase of contact pressure suggested potential cartilage damages. In terms of the kinematic alterations, the tibia moved more posteriorly and internally with respect to the femur. And, the displacement in the medial-lateral direction reversed. In addition, the sharp force increase in the anterior cruciate ligament explained the reason why meniscal and anterior cruciate ligament injuries always happened concurrently. And, the anterior lateral ligament may act as the stabilizer in the tibial posterior displacement and varus rotation.

INTERPRETATION

This study shows that menisci served as the joint load distribution, and also as the kinematics constraints in the posterior and medial-lateral direction, which is beneficial to the rehabilitation plan-making of meniscal injuries.

Biomechanical Stimulus Based Strategies for Meniscus Tissue Engineering and Regeneration

Meniscus injuries are very common in the knee joint. Treating a damaged meniscus continues to be a scientific challenge in sport medicine because of its poor self-healing potential and few clinical therapeutic options. Tissue engineering strategies are very promising solutions for repairing and regenerating a damaged meniscus. Meniscus is exposed to a complex biomechanical microenvironment, and it plays a crucial role in meniscal development, growth, and repairing. Over the past decades, increasing attention has been focused on the use of biomechanical stimulus to enhance biomechanical properties of the engineered meniscus. Further understanding the influence of mechanical stimulation on cell proliferation and differentiation, metabolism, relevant gene expression, and pro/anti-inflammatory responses may be beneficial to enhance meniscal repair and regeneration. On the one hand, this review describes some basic information about meniscus; on the other hand, we sum up the various biomechanical stimulus based strategies applied in meniscus tissue engineering and how these factors affect meniscal regeneration. We hope this review will provide researchers with inspiration on tissue engineering strategies for meniscus regeneration in the future.

Medial meniscus grafting restores normal tibiofemoral contact pressures

BACKGROUND

Tissue excision in the setting of a meniscal tear has been shown to dramatically increase peak contact stresses in the affected tibiofemoral joint compartment, leading to the development of degenerative changes and osteoarthritis.

PURPOSE/HYPOTHESIS

The current in vitro study utilized a porcine model to evaluate the effectiveness of segmental medial meniscal grafting following partial meniscectomy. The study hypothesis was that the procedure would normalize medial tibofemoral joint compartment pressure magnitudes, areas, and locations relative to an intact meniscus.

STUDY DESIGN

Controlled laboratory study.

METHODS

Using pressure film, medial tibiofemoral joint compartment peak, and mean pressure magnitudes, peak pressure location and peak pressure area were determined using 12 potted, fresh frozen, porcine knee specimens. Data were collected at three different knee flexion angles (90°, 45°, and 0°) for three conditions: intact medial meniscus, following resection of the central third of the medial meniscus, and following segmental medial meniscal grafting. For each condition, the potted femur was positioned horizontally in a bench vise clamp, while a 20 pound (88.96 N) axial compression force was manually applied for a 60 s duration by the primary investigator through the base of the potted tibia using a digital force gauge.

RESULTS

Loss of the central 1/3 of the medial meniscus resulted in significant increases in the mean and peak pressures of the medial tibiofemoral joint compartment and decreased peak pressure area. Segmental meniscal grafting of the central third defect closely recreated the contact pressures and loading areas of the native, intact medial meniscus.

CONCLUSION

From a static, time zero biomechanical perspective, segmental medial meniscus grafting of a partially meniscectomized knee restored mean pressure, peak pressure, and mean peak contact pressure areas of the medial tibiofemoral joint compartment back to levels observed in the intact medial meniscus at different knee flexion angles. In-vivo analysis under dynamic conditions is necessary to verify the healing efficacy and ability of the healed segmental medial meniscal allograft to provide long-term knee joint homeostasis when confronted with dynamic shear, rotatory, and combined, higher magnitude physiologic loading forces.

All-Inside Meniscus Repair Method for Injury of the Margin of the Anterior Segment of the Meniscus

Although the outside-in method has been used to treat injuries to the anterior segment of the meniscus, this method has drawbacks including the need to make a skin incision and portals for arthroscopy, pain caused by strangulation of the subcutaneous tissue and joint capsule, and protrusion of the knots. To resolve these problems, we present an all-inside method that enables simple suture of injuries to the anterior segment of the meniscus through arthroscopic portals placed only on the anteromedial and lateral sides without using a specific instrument. This simple, low-cost, low-invasive technique may be useful for suturing marginal injuries to the anterior segment of the meniscus.

In Vivo Tibial Cartilage Strains in Regions of Cartilage-to-Cartilage Contact and Cartilage-to-Meniscus Contact in Response to Walking

BACKGROUND

There are currently limited human in vivo data characterizing the role of the meniscus in load distribution within the tibiofemoral joint. Purpose/Hypothesis: The purpose was to compare the strains experienced in regions of articular cartilage covered by the meniscus to regions of cartilage not covered by the meniscus. It was hypothesized that in response to walking, tibial cartilage covered by the meniscus would experience lower strains than uncovered tibial cartilage.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Magnetic resonance imaging (MRI) of the knees of 8 healthy volunteers was performed before and after walking on a treadmill. Using MRI-generated 3-dimensional models of the tibia, cartilage, and menisci, cartilage thickness was measured in 4 different regions based on meniscal coverage and compartment: covered medial, uncovered medial, covered lateral, and uncovered lateral. Strain was defined as the normalized change in cartilage thickness before and after activity.

RESULTS

Within each compartment, covered cartilage before activity was significantly thinner than uncovered cartilage before activity ( P < .001). After 20 minutes of walking, all 4 regions experienced significant cartilage thickness decreases ( P < .01). The covered medial region experienced significantly less strain than the uncovered medial region ( P = .04). No difference in strain was detected between the covered and uncovered regions in the lateral compartment ( P = .40).

CONCLUSION

In response to walking, cartilage that is covered by the meniscus experiences lower strains than uncovered cartilage in the medial compartment. These findings provide important baseline information on the relationship between in vivo tibial compressive strain responses and meniscal coverage, which is critical to understanding normal meniscal function.

Equine meniscal degeneration is associated with medial femorotibial osteoarthritis

BACKGROUND

There is limited information available concerning normal equine meniscal morphology, its degeneration and role in osteoarthritis (OA).

OBJECTIVES

To characterise normal equine meniscal morphology and lesions and to explore the relationship between equine meniscal degeneration and femorotibial OA.

STUDY DESIGN

Ex vivo cadaveric study.

METHODS

Menisci were harvested from 7 normal joints (n = 14 menisci) and 15 joints with OA (n = 30 menisci). A macroscopic femorotibial OA score (cartilage degeneration and osteophytosis) was employed to measure disease severity in each compartment. The femoral and tibial meniscal surfaces were scored for macroscopic fibrillation and tears (1-4). Histological sections (regions: cranial and caudal horn; body) were also scored for microscopic fibrillation and tears (0-3) and inner border degeneration (0-3).

RESULTS

Partial meniscal tears were present on both femoral and tibial surfaces in all 3 regions and most frequently identified on the femoral surface of the cranial horn of the medial meniscus and body of the lateral meniscus. There was a significantly positive correlation between the global medial meniscal macroscopic scores and osteophyte (r = 0.7, P = 0.002) or cartilage degeneration (r = 0.5, P = 0.03) scores within the medial femorotibial joint. The global medial meniscal macroscopic score was greater (P = 0.004) in the advanced OA joints compared with control joints.

MAIN LIMITATIONS

The menisci were principally from abattoir specimens without a known clinical history because of the challenge in obtaining a large number of specimens with a clinical diagnosis of femorotibial OA.

CONCLUSIONS

This study is the first to describe normal equine meniscal morphology and lesions. Meniscal lesions were identified in all segments and on both articular surfaces. Meniscal degeneration significantly correlated with OA severity in the equine medial femorotibial joint. The relationship between OA and meniscal pathology remains to be elucidated.

Influence of meniscus on cartilage and subchondral bone features of knees from older individuals: A cadaver study

Objective

Cartilage and subchondral bone form a functional unit. Here, we aimed to examine the effect of meniscus coverage on the characteristics of this unit in knees of older individuals.

Methods

We assessed the hyaline cartilage, subchondral cortical plate (SCP), and subchondral trabecular bone in areas covered or uncovered by the meniscus from normal cadaver knees (without degeneration). Bone cores harvested from the medial tibial plateau at locations uncovered (central), partially covered (posterior), and completely covered (peripheral) by the meniscus were imaged by micro-CT. The following were measured on images: cartilage volume (Cart.Vol, mm³) and thickness (Cart.Th, mm); SCP thickness (SCP.Th, μm) and porosity (SCP.Por, %); bone volume to total volume fraction (BV/TV, %); trabecular thickness (Tb.Th, μm), spacing (Tb.Sp, μm), and number (Tb.N, 1/mm); structure model index (SMI); trabecular pattern factor (Tb.Pf); and degree of anisotropy (DA).

Results

Among the 28 specimens studied (18 females) from individuals with mean age 82.8±10.2 years, cartilage and SCP were thicker at the central site uncovered by the meniscus than the posterior and peripheral sites, and Cart.Vol was greater. SCP.Por was highest in posterior samples. In the upper 1–5 mm of subchondral bone, central samples were characterized by higher values for BV/TV, Tb.N, Tb.Th, and connectivity (Tb.Pf), a more plate-like trabecular structure and lower anisotropy than with other samples. Deeper down, at 6–10 mm, the differences were slightly higher for Tb.Th centrally, DA peripherally and SMI posteriorly.

Conclusions

The coverage or not by meniscus in the knee of older individuals is significantly associated with Cart.Th, SCP.Th, SCP.Por and trabecular microarchitectural parameters in the most superficial 5 mm and to a lesser extent the deepest area of subchondral trabecular bone. These results suggest an effect of differences in local loading conditions. In subchondral bone uncovered by the meniscus, the trabecular architecture resembles that of highly loaded areas.

MR imaging of the anatomy of the anterior horn of the medial meniscus

Background In cadaveric and arthroscopic studies different insertion locations of the anterior horn of the medial meniscus (AHMM) have been described. Purpose To investigate if the different insertion locations of the AHMM, as described in cadaveric studies, can be determined on magnetic resonance imaging (MRI). Material and Methods MR images of 100 patients without meniscal tears on MRI were retrospectively evaluated. Two observers classified the AHMM insertion based on its position relative to the anterior tibial edge and the medial tibial spine. The association between AHMM insertion and tibial plateau slope, meniscal radial displacement, and anterior intermeniscal ligament (AIL) presence was investigated. Results The AHMM inserted posterior to the anterior tibial edge in 93 knees and anterior to the tibial edge in seven knees (= type III). Of the 93 knees with AHMM insertion posterior to the anterior tibial edge, 63 inserted lateral to the medial tibial spine (= type I) and 30 medial (= type II). The AHMMs inserting anterior to the tibial edge had a significantly ( P < 0.05) steeper anterior tibial plateau slope and a significantly ( P < 0.05) higher presence of the AIL. No significant difference in radial displacement was observed between the three insertion types ( P > 0.05). A strong inter- and intra-observer agreement was observed. Conclusion Three different bony insertion locations of the AHMM, as described in cadaveric studies, could be identified on MRI. All AHMMs inserting anterior to the tibial edge displayed an AIL. Whether there is a clinical correlation with these insertion patterns remains unclear.

High meniscal slope angle as a risk factor for meniscal allograft extrusion

A meniscal graft extrusion is still an unresolved problem that affects most patients after a meniscal transplantation. Despite the advances in surgical techniques, together with the improved methods for a meniscal allograft sizing, success is only observed in up to 75% of patients after they experience a meniscal allograft transplantation. Because a meniscal extrusion is associated with a cartilage deterioration and the progression of osteoarthritis there is a great interest in how to prevent this phenomenon. The crucial factor for the minimisation of a meniscal allograft extrusion is by perfectly matching the implant. Most methods for a meniscal allograft sizing only focus on assessing the length and the width of the meniscus. Even though there is some evidence that there is a relationship between the shape of the meniscus in a cross-sectional plane and the meniscal extrusion, any of the planning methods do not take this factor into consideration. Although there is a large variability of meniscus shapes in cross-section, we hypothesise that by taking the meniscal slope into account during surgical planning, as well as performing the correct adjustments of this particular parameter, we can diminish the risk of a meniscal allograft extrusion.

Osteoarthritis year in review 2016: mechanics

Inappropriate biomechanics, namely wear-and-tear, has been long believed to be a main cause of osteoarthritis (OA). However, this view is now being re-evaluated, especially when examined alongside mechanobiology and new biomechanical studies. These are multiscale experimental and computational studies focussing on cell- and tissue-level mechanobiology through to organ- and whole-body-level biomechanics, which focuses on the biomechanical and biochemical environment of the joint tissues. This review examined papers from April 2015 to April 2016, with a focus on multiscale experimental and computational biomechanical studies of OA. Assessing the onset or progression of OA at organ- and whole-body-levels, gait analysis, medical imaging and neuromusculoskeletal modelling revealed the extent to which tissue damage changes the view of inappropriate biomechanics. Traditional gait analyses studies reported that conservative treatments can alter joint biomechanics, thereby improving pain and function experienced by those with OA. Results of animal models of OA were consistent with these human studies, showing interactions among bone, cartilage and meniscus biomechanics and the onset and/or progression OA. Going down size scales, experimental and computational studies probed the nanosize biomechanics of molecules, cells and extracellular matrix, and demonstrated how the interactions between biomechanics and morphology affect cartilage dynamic poroelastic behaviour and pathways to OA. Finally, integration of multiscale experimental data and computational models were proposed to predict cartilage extracellular matrix remodelling and the development of OA. Summarising, experimental and computational methods provided a nuanced biomechanical understanding of the sub-cellular, cellular, tissue, organ and whole-body mechanisms involved in OA.

Matrix metalloproteinase activity and prostaglandin E2 are elevated in the synovial fluid of meniscus tear patients

PURPOSE

Meniscus tears are a common knee injury and are associated with the development of post-traumatic osteoarthritis (OA). The purpose of this study is to evaluate potential OA mediators in the synovial fluid and serum of meniscus tear subjects compared to those in the synovial fluid of radiographic non-OA control knees.

MATERIALS AND METHODS

Sixteen subjects with an isolated unilateral meniscus injury and six subjects who served as reference controls (knee Kellgren-Lawrence grade 0-1) were recruited. Twenty-one biomarkers were measured in serum from meniscus tear subjects and in synovial fluid from both groups. Meniscus tear subjects were further stratified by tear type to assess differences in biomarker levels.

RESULTS

Synovial fluid total matrix metalloproteinase (MMP) activity and prostaglandin E2 (PGE2) were increased 25-fold and 290-fold, respectively, in meniscus tear subjects as compared to reference controls (p < 0.05). Synovial fluid MMP activity and PGE2 concentrations were positively correlated in meniscus tear subjects (R = 0.83, p < 0.0001). In meniscus tear subjects, synovial fluid levels of MMP activity, MMP-2, MMP-3, sGAG, COMP, IL-6, and PGE2 were higher than serum levels (p < 0.05). Subjects with complex meniscus tears had higher synovial fluid MMP-10 (p < 0.05) and reduced serum TNFα and IL-8 (p < 0.05) compared to other tear types.

CONCLUSIONS

Given the degradative and pro-inflammatory roles of MMP activity and PGE2, these molecules may alter the biochemical environment of the joint. Our findings suggest that modulation of PGE2 signaling, MMP activity, or both following a meniscus injury may be targets to promote meniscus repair and prevent OA development.

The Influence of Articular Cartilage Thickness Reduction on Meniscus Biomechanics

OBJECTIVE

Evaluation of the biomechanical interaction between meniscus and cartilage in medial compartment knee osteoarthritis.

METHODS

The finite element method was used to simulate knee joint contact mechanics. Three knee models were created on the basis of knee geometry from the Open Knee project. We reduced the thickness of medial cartilages in the intact knee model by approximately 50% to obtain a medial knee osteoarthritis (OA) model. Two variants of medial knee OA model with congruent and incongruent contact surfaces were analysed to investigate the influence of congruency. A nonlinear static analysis for one compressive load case was performed. The focus of the study was the influence of cartilage degeneration on meniscal extrusion and the values of the contact forces and contact areas.

RESULTS

In the model with incongruent contact surfaces, we observed maximal compressive stress on the tibial plateau. In this model, the value of medial meniscus external shift was 95.3% greater, while the contact area between the tibial cartilage and medial meniscus was 50% lower than in the congruent contact surfaces model. After the non-uniform reduction of cartilage thickness, the medial meniscus carried only 48.4% of load in the medial compartment in comparison to 71.2% in the healthy knee model.

CONCLUSIONS

We have shown that the change in articular cartilage geometry may significantly reduce the role of meniscus in load transmission and the contact area between the meniscus and cartilage. Additionally, medial knee OA may increase the risk of meniscal extrusion in the medial compartment of the knee joint.

Anterior Horn Meniscal Repair Using an Outside-In Suture Technique

The menisci are important structures within the knee that play a critical role in maintaining proper stability, load distribution, and joint lubrication. Injury to the menisci has been found to significantly alter the complex biomechanics of the knee, and thus affect the health and longevity of the native joint. Tears involving the anterior horn are increasingly recognized as an important pathology. Although early treatment of meniscal tears focused primarily on removal of the injured tissue, recent attention on the long-term consequences of partial or total meniscectomy has led to increased attempts at meniscus repair whenever possible. Because of the location of anterior horn tears and the technical difficulty in accessing this location arthroscopically, an outside-in repair technique is ideal for treatment of these lesions. This technical note details our surgical technique of outside-in repair of anterior horn meniscal tears.

Novel organ-slice culturing system to simulate meniscal repair: Proof of concept using a synovium-based pool of meniscoprogenitor cells

Meniscal injuries can occur secondary to trauma or be instigated by the changes in knee-joint function that are associated with aging, osteo- and rheumatoid arthritis, disturbances in gait, and obesity. Sixty percent of persons over 50 years of age manifest signs of meniscal pathology. The surgical and arthroscopic measures that are currently implemented to treat meniscal deficiencies bring only transient relief from pain and effect but a temporary improvement in joint function. Although tissue-engineering-based approaches to meniscal repair are now being pursued, an appropriate in-vitro model has not been conceived. The aim of this study was to develop an organ-slice culturing system to simulate the repair of human meniscal lesions in vitro. The model consists of a ring of bovine meniscus enclosing a chamber that represents the defect and reproduces its sequestered physiological microenvironment. The defect, which is closed with a porous membrane, is filled with fragments of synovial tissue, as a source of meniscoprogenitor cells, and a fibrin-embedded, calcium-phosphate-entrapped depot of the meniscogenic agents BMP-2 and TGF-β1. After culturing for 2 to 6 weeks, the constructs were evaluated histochemically and histomorphometrically, as well as immunohistochemically, for the apoptotic marker caspase 3 and collagen types I and II. Under the defined conditions, the fragments of synovium underwent differentiation into meniscal tissue, which bonded with the parent meniscal wall. Both the parent and the neoformed meniscal tissue survived the duration of the culturing period without significant cell losses. The concept on which the in-vitro system is based was thus validated. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1588-1596, 2016.

Viscoelastic properties of rabbit osteoarthritic menisci: A correlation with matrix alterations

The aim of this study was to evaluate the effect of early osteoarthritis (OA) on the viscoelastic properties of rabbit menisci and to correlate the mechanical alterations with the microstructural changes. Anterior Cruciate Ligament Transection (ACLT) was performed in six male New-Zealand White rabbits on the right knee joint. Six healthy rabbits served as controls. Menisci were removed six weeks after ACLT and were graded macroscopically. Indentation-relaxation tests were performed in the anterior and posterior regions of the medial menisci. The collagen fibre organization and glycosaminoglycan (GAG) content were assessed by biphotonic confocal microscopy and histology, respectively. OA menisci displayed severe macroscopic lesions compared with healthy menisci (p=0.009). Moreover, the instantaneous and equilibrium moduli, which were 2.9±1.0MPa and 0.60±0.18MPa in the anterior region of healthy menisci, respectively, decreased significantly (p=0.03 and p=0.004, respectively) in OA menisci by 55% and 57%, respectively, indicating a global decrease in meniscal stiffness in this region. The equilibrium modulus alone decreased significantly (p=0.04) in the posterior region, going from 0.60±0.18MPa to 0.26±012MPa. This induced a loss of tissue elasticity. These mechanical changes were associated in the posterior region with a structural disruption of the superficial layers, from which the tie fibres emanate, and with a decrease in the GAG content in the anterior region. Consequently, the circumferential collagen fibres of the deep zone were dissociated and the collagen bundles were less compact. Our results demonstrate the strong meniscal modifications induced by ACLT at an early stage of OA and highlight the relationship between structural and chemical matrix alterations and mechanical properties.

Effect of Human Serum and 2 Different Types of Platelet Concentrates on Human Meniscus Cell Migration, Proliferation, and Matrix Formation

PURPOSE

To evaluate the effect of 10% human serum (HS), 5% platelet-rich plasma (PRP), and 5% autologous conditioned plasma (ACP) on migration, proliferation, and extracellular matrix (ECM) synthesis of human meniscus cells.

METHODS

Cell migration and proliferation on stimulation with HS, PRP, and ACP were assessed by chemotaxis assays and measurement of genomic DNA content. Meniscus cells were cultivated in pellets stimulated with 10% HS, 5% PRP, or 5% ACP. Meniscal ECM formation was evaluated by histochemical staining of collagen type I, type II, and proteoglycans and by analysis of fibrochondrocyte marker gene expression.

RESULTS

Human meniscus cells were significantly attracted by all 3 blood-derived products (10% HS and 5% ACP: P = .0001, 5% PRP: P = .0002). Cell proliferation at day 9 was significantly increased on stimulation with 10% HS (P = .0001) and 5% PRP (P = .0002) compared with 5% ACP and controls. Meniscus cell pellet cultures showed the formation of a well-structured meniscal ECM with deposition of collagen type I, type II, and proteoglycans on stimulation with 10% HS, whereas 5% PRP or 5% ACP resulted in the formation of an inhomogeneous and more fibrous ECM. Stimulation with 10% HS and 5% ACP showed a significant induction of fibrochondrocyte marker genes such as aggrecan (HS: P = .0002, ACP: P = .0147), cartilage oligomeric matrix protein (HS: P = .0002, ACP: P = .0005), and biglycan (HS: P = .0002, ACP: P = .0003), whereas PRP showed no inducing effect.

CONCLUSIONS

Among all tested blood-derived products, only stimulation with HS showed the formation of a meniscal ECM as well as positive cell proliferating and migrating effects in vitro. Regarding a potential biological repair of nonvascular meniscus lesions, our results may point toward the use of HS as a beneficial augment in regenerative meniscus repair approaches.

CLINICAL RELEVANCE

Our findings may suggest that HS might be a beneficial augment for meniscus repair.

Incidence of and Factors Associated With the Decision to Undergo Anterior Cruciate Ligament Reconstruction 1 to 10 Years After Injury

BACKGROUND

Among patients treated nonoperatively for 1 year after anterior cruciate ligament (ACL) disruption, little is known about the frequency of ACL reconstruction within the first year of injury and the effect of age range, sex, and meniscal tears on the incidence of ACL reconstruction between 1 and 10 years after injury.

PURPOSE

To (1) define the rate of delayed ACL reconstruction (between 1 and 10 years after injury) in a population-based cohort of isolated ACL tears and (2) evaluate predictive factors associated with delayed reconstruction.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

The study included a population-based cohort of 1841 patients with new-onset, isolated ACL tears that occurred between January 1, 1990, and December 31, 2010. The complete medical records were reviewed to confirm diagnosis and collect data on clinical characteristics and details of subsequent ACL surgery. To evaluate the incidence of ACL reconstruction between 1 and 10 years after injury, landmark survival analysis was performed with a landmark set at 1 year after injury. Early and late predictors of ACL reconstruction were analyzed using Cox proportional hazards regression.

RESULTS

A total of 661 patients were treated nonoperatively for the first year after ACL tears. Over a mean 10 years of follow-up, 213 patients (32%) underwent ACL reconstruction between 1 and 10 years after injury. Young age (hazard ratio [HR], 0.55 per decade increase in age; 95% CI, 0.48-0.62) and meniscal tear at injury (HR, 1.48; 95% CI, 1.12-1.95) were significant predictors of undergoing delayed reconstruction. The rate of delayed ACL reconstruction decreased significantly over the study period (P < .03). There was no association between sex (HR, 0.89; 95% CI, 0.67-1.16) and delayed ACL reconstruction. Among patients who had delayed ACL reconstruction, 40% experienced a secondary meniscal tear before surgery.

CONCLUSION

In this study population of 1841 patients, 62% of patients received ACL reconstruction within 1 year of injury. Of patients treated nonoperatively for 1 year after ACL tears, 32% underwent delayed ACL reconstruction. Predictors of reconstruction beyond 1 year were young age (50% reduction in reconstruction per decade increased age) and baseline meniscal tear. Sex was not predictive for reconstruction beyond 1 year from injury.

Osteoarthritis year in review 2015: mechanics

Motivated by the conceptual framework of multi-scale biomechanics, this narrative review highlights recent major advances with a focus on gait and joint kinematics, then tissue-level mechanics, cell mechanics and mechanotransduction, matrix mechanics, and finally the nanoscale mechanics of matrix macromolecules. A literature review was conducted from January 2014 to April 2015 using PubMed to identify major developments in mechanics related to osteoarthritis (OA). Studies of knee adduction, flexion, rotation, and contact mechanics have extended our understanding of medial compartment loading. In turn, advances in measurement methodologies have shown how injuries to both the meniscus and ligaments, together, can alter joint kinematics. At the tissue scale, novel findings have emerged regarding the mechanics of the meniscus as well as cartilage superficial zone. Moving to the cell level, poroelastic and poro-viscoelastic mechanisms underlying chondrocyte deformation have been reported, along with the response to osmotic stress. Further developments have emerged on the role of calcium signaling in chondrocyte mechanobiology, including exciting findings on the function of mechanically activated cation channels newly found to be expressed in chondrocytes. Finally, AFM-based nano-rheology systems have enabled studies of thin murine tissues and brush layers of matrix molecules over a wide range of loading rates including high rates corresponding to impact injury. With OA acknowledged to be a disease of the joint as an organ, understanding mechanical behavior at each length scale helps to elucidate the connections between cell biology, matrix biochemistry and tissue structure/function that may play a role in the pathomechanics of OA.

WITHDRAWN: Meniscus mechanics and mechanobiology

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.1016/j.jbiomech.2015.03.020. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.